The invention relates to an electro-erosive machining apparatus of the sort comprising at least one tool electrode and one workpiece electrode which are arranged to move relative to each other in a first operating direction and in a second operating direction involving the performance of a translatory rotational motion in a plane transverse to the first operating direction, driving and controlling devices for moving the electrodes in the first and second directions and means coordinating the driving and controlling means for moving the electrodes so as to determine the shaping of multidimensional surfaces to be formed within the workpiece electrode.
An apparatus of this kind, in the form of a spark-eroding machine, is known from Swiss Pat. No. 596,940. This machine accomplishes a three-dimensional relative, operating movement of the tool-electrode (hereinafter "electrode") and of the workpiece-electrode (hereinafter "workpiece") in the form of a translatory rotational motion with variable radial deflection in a plane, and an axial displacement in a direction transverse to the plane which is a function of the radial deflection.
In the known machining apparatus, separate adjusting motors, with appropriate drive-controls and a superimposed control-system, are provided for the various axes of the spatial coordinates-system and the corresponding components of the relative operating movement between the electrode and the workpiece. This makes it possible to achieve generally cylindrical and conical surfaces as envelope-surfaces on the workpiece, in addition to three dimensional surfaces meeting certain conditions of symmetry, more paticularly spherical surfaces.
In the case of modern spark-erosion machining methods, however, there arises the problem of producing extensive workpiece surface envelopes or electrode-motion surface envelopes by a sequence of operating increments corresponding to an operating movement occurring on surfaces which are conical or sloping in relation to the main feed direction. Such a complex machining method in which the shaped surface represents the envelope-surface of the operating increments requires control functions for the feed along individual coordinate axes which cannot be obtained with the known apparatus. This also applies to specific, substantially two-dimensional operating movements requiring, instead of a continuous rotary motion, selective setting of specific angular positions within the rotary motion A complex method of operation of the type mentioned above also occurs in the case of operating movements which take place in a specific axial-radial plane, for example, when progressive operating increment steps are arranged in rows or are superimposed, for example, a comparatively small incremetal lift with an electrode feed at an angle to the axial and radial directions. Here again, the final shape of the surface is determined by the envelope or tangential surface of the electrode-surface-points in their maximal gap position.